Xuéxí líhécí shì zhōngjí Hànyǔ yǔfǎ de nándiǎn zhī yī.
Learning separable words is one of the trickiest points of intermediate Chinese grammar.
Tips
grammar
Common examples: 见面 → 见过一次面, 帮忙 → 帮了我的忙, 跳舞 → 跳了一场舞, 结婚 → 结过婚. The verbal element comes first; aspect markers (了, 过), measure phrases and modifiers slot between the two halves.
mistakes
Wrong: ✗ 我见面了他. Right: ✓ 我见了他一面 / 我跟他见了面. Anything that would normally come after a regular verb (object, duration, frequency) goes between the two halves of the 离合词, not after the whole thing.